Structural and electrical properties of sol–gel-derived Al-doped bismuth ferrite thin films

Al-doped BiFeO3 (BiFe(1−x)AlxO3) thin films with small doping content (x=0, 0.05, and 0.1) were grown on Pt(111)/TiO2/SiO2/Si substrates at the annealing temperature of 550 °C for 5 min in air by the sol–gel method. The crystalline structure, as well as surface and cross section morphology were studied by X-ray diffraction and scanning electron microscope, respectively. The dielectric constant of BiFeO3 film was approximately 71 at 100 kHz, and it increased to 91 and 96 in the 5% and 10% Al-doped BiFeO3 films, respectively. The substitution of Al atoms in BiFeO3 thin films reduced the leakage current obviously. At an applied electric field of 260 kV/cm, the leakage current density of the undoped BiFeO3 films was 3.97×10−4 A/cm2, while in the 10% Al-substitution BiFeO3 thin films it was reduced to 8.4×10−7 A/cm2. The obtained values of 2Pr were 63 μC/cm2 and 54 μC/cm2 in the 5% and 10% Al-doped BiFeO3 films at 2 kHz, respectively.